Method for manufacturing and device for manufacturing ultrafine fiber nonwoven fabric

ABSTRACT

A spinning die for producing ultrafine fiber nonwoven fabric is made miniaturized and its productivity thereof is enhanced. The spinning die has a substantial cuboid shape and a plurality of nozzle holes is disposed in a longitudinal direction. A slit for jetting hot air is disposed only in one side of the nozzle holes. Thermoplastic polymer is melt blown from the nozzle of the spinning die to obtain ultrafine fibers. Hot air is jetted from the slit disposed at only one side of the nozzle holes. The result is that the ultrafine fibers melt blown in a direction inclined with respect to an axis direction of the nozzle. The blown ultrafine fibers are accumulated by sucking to downward to obtain ultrafine fiber nonwoven fabric.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a National Phase application filed under 35 USC 371of PCT International Application No. PCT/JP2016/070580 with anInternational Filing Date of Jul. 12, 2016, which claims under 35 U.S.C.§ 119(a) the benefit of Japanese Application No. 2015-144966 filed onJul. 22, 2015, the entire contents of which are incorporated herein byreference.

BACKGROUND (a) Technical Field

The present disclosure relates to a method for producing ultrafine fiber(or filament) nonwoven fabric and an apparatus therefor, in particularto the method which has excellent productivity and the apparatustherefor with a reduced size.

(b) Description of the Related Art

Hitherto, ultrafine fiber nonwoven fabric has been produced with using aspinning die of a substantial cuboid shape, which has nozzle holes formelt blowing thermoplastic polymer and slits for jetting hot air in bothsides of the nozzle holes. The nozzle holes are linearly arranged in alongitudinal direction of the substantial cuboid spinning die. Thespinning die is set to adjust the longitudinal direction of the spinningdie to a width direction of the ultrafine fiber nonwoven fabric. A lotof ultrafine fibers are blown from the nozzle holes and accumulated toform ultrafine fiber nonwoven fabric.

A schematic cross sectional view of the spinning die is shown in FIG. 1.The longitudinal direction of the spinning die 1 is the direction fromthe front side to the back side of the paper sheet on which FIG. 1 isdrawn. A plurality of nozzle holes 2 are aligned in a determined spacedistance along the longitudinal direction of the spinning die 1 (thedirection from the front side to the back side of the paper sheet).Molten thermoplastic polymer is flowed from a polymer passage 3 todownward, and passed through an upper end of a nozzle to reach thenozzle hole 2. Hot air is flowed in pipes 6, 6 in a pressurizedcondition and passed through hot air passages 5, 5 to jet from slits 4,4 which are disposed to both side of the nozzle hole 2. Thus, the moltenthermoplastic polymer at the nozzle hole 2 is blown to a direction of anaxis line of the nozzle with hot air jetted from the slits 4, 4 toobtain ultrafine fibers. A spinning die similar to the above isdisclosed in Japanese Publication 2015-14065.

However, the spinning die 1 needs to have the pipes 6, 6, the hot airpassages 5, 5 and the slits 4, 4 in both sides of the nozzle hole, toresult in a drawback of a large-sized apparatus. The object of thepresent disclosure is to overcome the drawback and to make a small-sizedapparatus. In addition, the spinning die is small-sized and a pluralityof the spinning dies may be arranged in parallel, thus a productivity ofultrafine fiber nonwoven fabric may be enhanced.

SUMMARY

In order to solve the above problems, according to the presentdisclosure, it is not always necessary to include the slits in bothsides of the nozzle hole. Accordingly, the reason why the conventionalspinning die includes the slits in both sides of the nozzle hole isconsidered that the thermoplastic polymer is melt blown from the nozzlehole 2 by jetting hot air to the axis direction of the nozzle and themelt blown ultrafine fiber is extended to the direction of the axis toenhance the strength of the ultrafine fiber. However, it has been foundthat, even if hot air is jetted to the direction of axis of theultrafine fiber in the condition, because the ultrafine fiber isfloating in the air, almost no extension effects of the fiber areobtained.

Accordingly, in the present disclosure, hot air has been jetted fromonly one side of the nozzle hole to produce ultrafine fiber nonwovenfabric, and it was found that the resultant ultrafine fiber nonwovenfabric has almost the same properties as the conventional ultrafinefiber nonwoven fabric. Thus, the present disclosure provides a methodfor producing ultrafine fiber nonwoven fabric, which comprises: a stepof melt blowing thermoplastic polymer from a plurality of nozzle holeswhich are disposed in a longitudinal direction at a longitudinal lowerend of a spinning die having a substantial cuboid shape to obtainultrafine fibers, a step of jetting out hot air from a slit disposed inonly one side of the nozzle holes to blow the ultrafine fibers at anangle inclining with respect to the direction of an axial line of thenozzles, and a step of accumulating the blown ultrafine fibers which aresucked downward from the spinning die to form the ultrafine fibernonwoven fabric.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a schematic cross sectional view of a conventional spinningdie for a producing apparatus for ultrafine fiber nonwoven fabric.

FIG. 2 shows a schematic cross sectional view of an example of thespinning die employed in the producing apparatus for the ultrafine fibernonwoven fabric of the present invention.

FIG. 3 is a conceptual diagram showing a relation of an axial line ofthe nozzle with a blowing direction of the ultrafine fiber or a jettingdirection of hot air.

FIG. 4 shows a schematic cross sectional view of another embodiment ofthe spinning die employed in the producing apparatus for the ultrafinefiber nonwoven fabric of the present invention. FIG. 5 shows a schematiccross sectional view of the producing apparatus of ultrafine fibernonwoven fabric, which combines two of the spinning dies of FIG. 2.

FIG. 6 shows a schematic cross sectional view of the producing apparatusof ultrafine fiber nonwoven fabric, which combines two of the spinningdies of FIG. 4.

FIG. 7 shows a schematic cross sectional view of the producing apparatusof ultrafine fiber nonwoven fabric, which combines the spinning die ofFIG. 2 with the spinning die of FIG. 4, in which the jetting directionsof hot air are faced with each other.

FIG. 8 shows a schematic cross sectional view of the producing apparatusof ultrafine fiber nonwoven fabric, which combines the spinning die ofFIG. 2 with the spinning die of FIG. 4, in which the jetting directionsof hot air are leaving apart with each other.

DETAILED DESCRIPTION OF THE DISCLOSURE

The production method of the present disclosure is conducted with usinga specific spinning die. The specific spinning die may include anembodiment shown in FIG. 2. FIG. 2 shows a schematic cross sectionalview of a spinning die having a cuboid shape and a direction from thefront side to the back side of the paper sheet on which FIG. 2 is drawnis a longitudinal direction of the spinning die 1. A plurality of nozzleholes 2 are aligned in the longitudinal direction (the direction fromthe front side to the back side of the paper sheet) in a determinedspace distance. Thermoplastic polymer is melt blown from the nozzleholes to form ultrafine fibers.

A slit is provided in only a right side of the nozzle hole 2. Hot air isflowed in pipes 6 in a pressurized condition and passed through hot airpassage 5, thus jetting from slit 4. Accordingly, the ultrafine fibersfrom the nozzle 2 are blown to a left side to the axis line direction ofthe nozzle by jetting hot air. FIG. 3 schematically shows the directionof the axis line of the nozzle and the direction of blowing ultrafinefibers. The direction of blowing ultrafine fibers inclines a determinedangle of θ with respect to the direction of the axis line of the nozzle.The angle of θ can be any value and may generally be preferred to bewithin a range of 30° to 60°. For setting an angle of the direction ofblowing ultrafine fibers to θ, it is needless to say that a jettingangle of hot air is made θ with respect to the direction of the axisline of the nozzle.

Hot air is jetted to the ultrafine fibers at an angle of θ incliningwith respect to the direction of the axis line of the nozzle. In thisair jetting, it is necessary that the ultrafine fibers are suckeddownward of the spinning die 1. Without sucking, it is not so easy thatthe ultrafine fibers are uniformly accumulated on a conveyer providedunder the spinning die 1, thus deteriorating qualities of the resultantultrafine fiber nonwoven fabric. The sucking can generally be conductedby a reduced pressure using a suction box from a lower portion of abreathable conveyer, such as a wire mesh chain conveyer and the like.

In FIG. 2 the slit is disposed in only a right side of the nozzle hole2, but it can be disposed only in a left side. Accordingly, the die issymmetrical with the spinning die of FIG. 2 and its cross sectional viewis shown in FIG. 4 as a spinning die 1 using same number.

The apparatus for the production method of the present disclosure iscomprised of the spinning die 1 shown in FIG. 2 and/or FIG. 4.Accordingly, the spinning die 1 comprises a pipe for providing hot airand a passage for providing thermoplastic polymer.

Actually, the production of the ultrafine fiber nonwoven fabric may beconducted by an apparatus of only one of the spinning die 1 as shown inFIG. 2 or FIG. 4, or an apparatus of a combination of more than twospinning dies 1 shown in FIG. 2 (for example as shown in FIG. 5). It mayalso be conducted by an apparatus of a combination of more than twospinning dies of shown in FIG. 4 (for example as shown in FIG. 6). Inaddition, it may be an apparatus of a combination of the spinning die 1shown in FIG. 2 and the spinning die 1 shown in FIG. 4 (for example asshown in FIG. 7 and FIG. 8). The combined apparatus shown in FIG. 7 hasthe jetting directions of hot air, which are faced with each other. Thecombined apparatus shown in FIG. 8 has the jetting directions of hotair, which are left apart with each other. Further, the combinedapparatus can be assembled with two or more apparatuses or can bemanufactured as one body.

The term “ultrafine fiber” as used herein means fiber having a fiberdiameter of about 1 to about 15 μm. The thermoplastic polymer employedherein can be polyolefin, polyamide, polyester or the like. The nozzlehole 2 can generally have a diameter of about 0.1 to about 0.5 mm.Number of the nozzle holes can be 30 to 100 dies/inch and the nozzleholes are arranged in a longitudinal direction at a longitudinal lowerend of a spinning die 1. The nozzle generally has a length of about 1 toabout 5 mm.

In the combined apparatus of the present disclosure, a mixed ultrafinefiber nonwoven fabric can be obtained by changing the sorts of thethermoplastic polymer melt blown from each of the apparatuses. Forexample, polyester fiber is melt blown from one of the combinedapparatus and polypropylene is melt blown from the other of the combinedapparatus, thus obtaining a polyester/polypropylene ultrafine fibernonwoven fabric. In the combined apparatus of the present disclosure,another mixed ultrafine fiber nonwoven fabric can be obtained bychanging each diameter of the nozzle hole 2, thus obtaining a ultrafinefiber nonwoven fabric having different fiber diameter. For example, athermoplastic polymer is melt blown from one of the combined apparatuswhich provides nozzle holes having a diameter of 0.1 mm and athermoplastic polymer is melt blown from the other of the combinedapparatus which provides nozzle holes having a diameter of 0.5 mm, thusobtaining a ultrafine fiber nonwoven fabric having a mixed fiberdiameter.

The ultrafine fiber nonwoven fabric obtained by the production method ofthe present disclosure can be used for applications, such as filtermaterial, cleaning cloth or the like.

The apparatus of the present disclosure has technical effects of makingit miniaturized because it has the pipe flowing hot air, the passage forhot air and the slit only in one side of the nozzle holes, as it isclear when comparing with the conventional apparatus of FIG. 1. Inaddition, even if two of the apparatuses of the present disclosure arecombined, the resulting combined apparatus has the same size with theconventional apparatus. According, the present disclosure has excellenttechnical effects in that the productivity of the ultrafine fibernonwoven fabric of the present disclosure can be double in comparisonwith that of the conventional apparatus.

What is claimed is:
 1. A method for producing ultrafine fiber nonwovenfabric, comprising: a step of melt blowing thermoplastic polymer from aplurality of nozzle holes which are disposed in a longitudinal directionat a longitudinal lower end of a spinning die having a substantialcuboid shape to obtain ultrafine fibers, a step of jetting out hot airfrom a slit disposed in only one side of the nozzle holes to blow theultrafine fibers at an angle inclining with respect to the direction ofan axial line of the nozzles, and a step of accumulating the blownultrafine fibers which are sucked downward from the spinning die to formthe ultrafine fiber nonwoven fabric.
 2. The method for producingultrafine fiber nonwoven fabric according to claim 1, wherein the slitis provided in either a right side or a left side of a line of thenozzle holes.
 3. The method for producing ultrafine fiber nonwovenfabric according to claim 1, wherein the ultrafine fibers are blown withhot air at an angle inclining 30° to 60° with respect to the axis lineof the nozzles.
 4. An apparatus for producing ultrafine fiber nonwovenfabric, comprising a plurality of nozzle holes disposed in alongitudinal direction at a longitudinal lower end of a spinning diehaving a substantial cuboid shape, and a slit for jetting hot airdisposed in only one side of a line of the nozzle holes.
 5. Theapparatus for producing ultrafine fiber nonwoven fabric according toclaim 5, wherein the slit is provided in only a right side of a line ofthe nozzle holes.
 6. The apparatus for producing ultrafine fibernonwoven fabric according to claim 5, wherein the slit is provided inonly a left side of a line of the nozzle holes.
 7. A combined apparatusfor producing ultrafine fiber nonwoven fabric is disposing at least twoof the apparatus according to claim 5 in parallel.
 8. A combinedapparatus for producing ultrafine fiber nonwoven fabric is disposing atleast two of the apparatus according to claim 6 in parallel.
 9. Acombined apparatus for producing ultrafine fiber nonwoven fabric ofclaim 4, further comprising a first apparatus in which the slit isprovided in only a right side of a line of the nozzle holes and a secondapparatus in which the slit is provided in only a left side of a line ofthe nozzle holes.
 10. The apparatus of producing ultrafine fibernonwoven fabric according to claim 4, wherein the hot air from the slitis jetted at an angle inclining 30° to 60° with respect to the axisdirection of the nozzles.